Dr. Y. Kuno summarized the results of extensive research on the human thermoregulatory effector system, heat stroke, and heat illness, and published the “Story about sweat” （1963）. To date, this book has been known as the bible for young investigators of the prevention of heat illness. However, today, some of the contents is inaccurate. In this article, we will introduce the “Story about sweat” （1968, 5 th edition） to compare/confirm new findings. As examples, 5 items are presented: 1. Exertional heat illness, including exercise-related heat illness, was defined as a state in which there is a >5℃ gap between skin and core temperatures in addition to a rectal temperature of >40℃. 2. In a hot environment, the most important function for thermoregulation during work or sports activities is heat loss by sweat secretion from sweat glands and its evaporation. 3. Sweating arrest is a danger signal of heat illness. 4. A desire for water is perceived as a sense of thirst. 5. An adequate criterion for the prevention of heat illness is whether the rate of weight loss is maintained at <2 to 3%. However, the rate of weight loss immediately after a race in a hot environment sometimes increases to 5 to 11% in elite marathon runners. This suggests an improvement in heat acclimation during routine training in elite runners.
